Safety valve structure has two categories: the spring-loaded, and leveraged. The spring-loaded sealing of valves and valve seat by a spring force. Leveraged rely on the forces of leverage and weight. With the large capacity needs, and have a pulse valve, also known as pilot safety valve, the main valve and auxiliary valve. When the medium pressure in the pipe exceeds a predetermined pressure value, the auxiliary valve is first turned on, the medium along the catheter into the main relief valve and the main relief valve to open, so that the increased pressure of the medium decreased.The safety valve emissions determines the diameter of the valve seat and the valve opening height, can be divided into two types: the opening height seat inside diameter (1/15) ~ (1/20), the entire Kai (1/3) to (1/4). In addition, with the use of different requirements, there are closed and not closed. Closed that the discharge of the media is not leaking, all along the required exit discharge are generally used for toxic and corrosive media. Not closed generally used for non-toxic and non-corrosive media.The hammer lever safety valve hammer and lever to balance the role of the force on the valve. According to the principle of leverage, it can use a smaller mass of the hammer via a lever increasing role to obtain a larger force, and to adjust the opening pressure of the safety valve by moving hammer position (or transform the weight of the mass).Hammer lever-type valve structure is simple, easy to adjust, but fairly accurate, the applied load due to an increase in the valve flap will not have a larger increase, applicable to high temperature of the occasion, in the past more commonly used, especially is used in the boiler and the higher temperature on the pressure vessel. The hammer lever safety valve structure is relatively bulky, easy vibration loading mechanism, and often leak due to vibration; their lower back seat pressure, not easily turned off and maintain a tight.Spring inching safety valve the use compression force of the spring to the balancing role in the force on the valve. Spiral coil spring compression by turning it. The adjusting nut to adjust the above, the use of this structure can be based on needs correcting the opening of the safety valve (tuning) pressure. Spring inching safety valve structure lightweight compact, high sensitivity, unrestricted installation location, and because of the sensitivity of the vibration is small, it can be used on mobile pressure vessel. The disadvantage of this safety valve is the applied load will change, i.e. with the opening of the valve, with the rise of the flap valve, the compression of the spring increases, the force acting on the valve flap also increase. This is detrimental to the rapid opening of the safety valve. In addition, the valve spring due to the long-term impact of high temperature of stretch reduced. Used in high temperature container, often to consider spring insulation or cooling issues, so that the structure becomes complicated.Pulse safety valve from the main valve and auxiliary valve, the main valve action by the pulse of the auxiliary valve driven, its complex structure, usually apply only to the safety discharge a lot of boilers and pressure vessels.